Hot press tool

ABSTRACT

A hot press tool for use in a hot press process is formed of at least one material selected from a group consisting of materials characterized by formula M n+1 AX n , wherein  
     M is an element selected from the group consisting of Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W;  
     A is an element selected from the group consisting of Al, Si, P, S, Ga, Ge, As, Cd, In, Sn, Tl, and Pb; and  
     X is an element selected from the group consisting of C and N.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a hot press tool for producingworkpieces by a hot process and formed of at least two elements.

[0003] 2. Description of the Prior Art

[0004] In the hot press process, workpieces are produced of a basicpowder material by using a powder metallurgical process, with formationof the workpieces with hot press tools under high pressure and hightemperature. Among the workpieces produced with the hot press processare, e.g., abrasive segments for annular bits.

[0005] The hot press tools, which are used in the hot press process, areusually formed of graphite and hard metal. A drawback of theconventional hot press tools formed of graphite is their lowwear-resistance and fracture-resistance. They also have a low oxidationresistance at high temperatures. The drawbacks of the hot press toolsformed of hard metals consist in their large weight, their difficultmachinability, and their limited temperature and oxidation resistance.Because of their low or limited oxidation resistance, the hot presstools are used under an inert atmosphere.

[0006] Accordingly, an object of the present invention is to provide ahot press tool that can be economically used under natural atmosphericconditions.

[0007] Another object of the present invention, is a hot press toolhaving a high wear-resistance and which is easily machinable.

SUMMARY OF THE INVENTION

[0008] These and other objects of the present invention, which willbecome apparent hereinafter, are achieved by forming a hot press tool ofat least one material selected from a group consisting of materialscharacterized by formula M_(n+1)AX_(n), wherein

[0009] M is an element selected from the group consisting of Sc, Ti, V,Cr, Zr, Nb, Mo, Hf, Ta, and W;

[0010] A is an element selected from the group consisting of Al, Si, P,S, Ga, Ge, As, Cd, In, Sn, Tl, and Pb; and

[0011] X is an element selected from the group consisting of C and N.

[0012] The compound M_(n+1)AX_(n) and its production in laboratoryamounts are known since 1967. The variable n preferably amounts from 1to 3. U.S. Pat. No. 5,942,455 discloses production of this compound inbulk amounts.

[0013] The materials of the compound M_(n+1)AX_(n) are ceramic materialsand, as such, have mechanical characteristics which do not depend ontemperatures. The hot press tools, which are produced from a compoundM_(n+1)AX_(n) have a high wear-resistant and are easily machinable. Thehigh oxidation resistance of the hot press tools, which are producedfrom compounds M_(n+1)AX_(n), at high temperatures permits to use thetools produced from these materials under natural atmosphericconditions. Moreover, by selecting appropriate elements and the variablen, the hot press tools, which are produced from the compoundM_(n+1)AX_(n) can be formed with an electrical conductance similar tothat of hard metal.

[0014] The hot press tools are produced from powder materials by using apowder metallurgical process in per se known manner with a desiredshape. The hot press tools can, e.g., be produced with a final shape anddimensions, i.e., be “net shaped.” Alternatively, the hot press tools,which are produced from a compound M_(n+1)AX_(n), can be produced in abasic form and be brought into a final form by subsequent processing.The hot press tools in a basic form can be then subjected toelectroerosion machining, grinding, drilling, sawing, etc.

[0015] The selection of the elements and the value of the stochiometriccoefficient of a compound M_(n+1)AX_(n) is based essentially on thepreferable characteristics of the hot press tool.

[0016] Advantageously, from the group M, Ti is selected, from the groupA, SI is selected, and from the group X, C is selected, which with apreferable variable n=2, permits to obtain a compound Ti₃SIC₂. The hotpress tool produced from this compound is characterized by aparticularly good mechanical characteristic.

[0017] Hot press tools with a particularly good oxidation resistance areobtained when from the group M, Ti is selected, from the group A, Al isselected, from group X, C is selected and n=1, which provides a materialTi₂AlC.

[0018] Hot press tools with a high electrical resistance are obtainedwhen from the group M, Ti is selected, from the group A, Al is selected,and from the group X, N is selected and n=3, i.e., the hot press toolsare produced from Ti₄AlN₃.

[0019] Advantageously, a hot press tool is essentially entirely producedfrom a material selected from a group of materials M_(n+1)AX_(n).However, a hot press tool can be produced only partially from thecompound M_(n+1)AX_(n). When several materials are used for producing ahot press tool, the material, which is selected from the groupM_(n+1)AX_(n), forms the outer surface or layer of the tool andconstitutes a percentage volume of the entire amount of materials.

[0020] Preferably, in hot press tool, the outer layer is formed of thecompound M_(n+1)AX_(n) which is applied to a base body. The base bodycan be formed, e.g., of a hard material on which a layer of a compoundM_(n+1)AX_(n) having an adequate thickness is deposited. The thicknessof the outer layer is determined by the required characteristics and byexisting conditions during the use of the hot press tool. With such ahot press tool, after the wear of the outer layer, a new layer can bedeposited on the base body. Thus, the based body can be used many times.

[0021] Advantageously, the hot press tool is formed as a punch and/orsleeve. The sleeve can be formed with a bottom, whereby a pot-shapedmember is produced. Also, other components of a hot press frame, suchas, e.g., dies, separation walls, pins, cores, screws, etc., can beproduced from a material selected from the group of materialsM_(n+1)AX_(n).

[0022] The novel features of the present invention, which are consideredas characteristic for the invention, are set forth in the appendedclaims. The invention itself, however both as to its construction andits mode of operation, together with additional advantages and objectsthereof, will be best understood from the following detailed descriptionof the preferred embodiments, when read with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings show:

[0024]FIG. 1 a schematic cross-sectional view of a hot press frame witha hot press tool according to the present invention;

[0025]FIG. 2 a perspective view of the punch shown in FIG. 1;

[0026]FIG. 3 a perspective view of the sleeve shown in FIG. 1;

[0027]FIG. 4 a perspective view of another embodiment of a punchaccording to the present invention; and

[0028]FIG. 5 a perspective view of another embodiment of a hot presstool according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] As discussed above, FIG. 1 shows schematically a partialcross-sectional view of a hot press frame 1 with a hot press toolaccording to the present invention. The hot press frame 1 includes a die2 with a plurality of recesses 3 (only one recess 3 is shown in thedrawing). The hot press tool according to the present invention isformed of three parts, a sleeve 4 which is located in the recess 3 andserves as a first hot press tool, a punch 5 which serves as a secondpress tool, and a bottom member 8 which is likewise located in therecess and which serves as a third hot press tool. With the formation ofthe hot press tool of three parts, a produced workpiece 6 is completelysurrounded by hot press tools forming the hot press tool according tothe present invention. This permits to produce the workpiece 6 undernatural atmospheric conditions. According to an embodiment of theinvention, the sleeve 4 can be formed integrally with the bottom member8 as a pot-shaped member.

[0030] A workpiece 6, which is produced by the hot press process, canbe, e.g., preliminary formed as a powered mold, as a cold-pressedworkpiece, or as a sintered part and then placed in the sleeve 4. Thepunch 5 is displaced in the direction shown with arrow 7 towards the die2 with a high pressure and at a high temperature until the workpiece 6is sufficiently compressed. Essentially, for producing the workpiece 6,a powder metallurgical process is used. When the die 2 is formed of amaterial selected from a group of material M_(n+1)AX_(n), thearrangement of the sleeve 4 in the recess 3 can be dispensed with, sothat the punch 5 would slide directly along the inner surface of therecess 3.

[0031] The punch 5, the sleeve 4 and, if necessary, the die 2 areproduced by using a powder metallurgical process of a material selectedfrom a group of a material characterized as it has already beendiscussed above, by formula M_(n+1)AX_(n). The elements of the hot presstool preferably are produced in a final form. However, the elements ofthe hot press tool can first be produced in a basic form and then beformed into a final form by using further processing steps, such ascutting, grinding, etc.

[0032] The punch 5, a perspective view of which is shown in FIG. 2, isformed as a circular cylinder the outer dimensions of which correspondto the inner dimensions of the sleeve 4 or to the inner dimensions ofthe recess 3. In order to insure a high resistance to oxidation and goodcharacteristics at high temperatures and good wear-resistance, the punch5 is produced, as discussed above, from a material selected from a groupof materials M_(n+1)AX_(n).

[0033]FIG. 3 shows, as discussed above, a perspective view of the sleeve4. The sleeve 4 has a tubular shape and has its dimensions adapted tothe outer dimension of the punch 5 and the inner dimension of the recess3. To insure the performance capability of the sleeve 4 as a hot presstool in the hot press frame, the sleeve 4, as the punch 5, is formed ofa material selected from the group of materials M_(n+1)AX_(n).

[0034]FIG. 4 shows another embodiment of the punch. The punch 11 has acylindrical basic body 12 provided with an outer layer 13 formed of amaterial selected from the group of materials M_(n+1)AX_(n). The basicbody can be formed, e.g., of a hard material.

[0035] A further embodiment of a combination hot press tool according tothe present invention is shown in FIG. 5. The tool has wall sections21.1 and 21.2 which as spaced from each other by separation walls 22.1and 22.2. A square-shaped punch (not shown) is introduced into space 23defined by the spaced from each other, separation walls 22.1 and 22.2.

[0036] The elements of the combination hot press tool are characterizedby their high mechanical characteristics and by flexibility of theirformation. It is to be noted that hot press tool having specific shapescan be economically produced. The hot press tool elements can beconnected with, e.g., screws which are likewise produced of a materialselected from the group of materials M_(n+1)AX_(n).

[0037] Examples of the materials of the group of materials M_(n+1)X_(n)are compounds TiSiC₂, Ti₂AlC, Ti₄AlN₃.

[0038] Though the present invention was shown and described withreferences to the preferred embodiments, such are merely illustrative ofthe present invention and are not to be construed as a limitationthereof and various modifications of the present invention will beapparent to those skilled in the art. It is therefore not intended thatthe present invention be limited to the disclosed embodiments or detailsthereof, and the present invention includes all variations and/oralternative of the present invention as defined by the

What is claimed is:
 1. A hot press tool for producing workpieces by ahot press process, wherein the hot press tool is formed of at least onematerial selected from a group consisting of materials characterized byformula M_(n+1)AX_(n), wherein M is an element selected from the groupconsisting of Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W; A is an elementselected from the group consisting of Al, Si, P, S, Ga, Ge, As, Cd, In,Sn, Tl, and Pb; and X is an element selected from the group consistingof C and N.
 2. A hot press tool according to claim 1, wherein theselected material is Ti₃SiC₂.
 3. A hot press tool according to claim 1,wherein the selected material is Ti₂AlC.
 4. A hot press tool accordingto claim 1, wherein the selected material is Ti₄AlN₃.
 5. A hot presstool according to claim 1, wherein the at least one material forms anouter layer (13) of the tool deposited on a base body (12).
 6. A hotpress tool according to claim 1, comprising at least one of a punch (5),(1) and a sleeve (4).